Optimization of some cations for removal of arsenic from groundwater by electrocoagulation process

This study dealt with investigation of arsenic removal from groundwater using electrocoagulation (EC) method in a batch mode by the Box-Behnken experimental design method. Effects of some cations like Ca, Fe, Mg, Mn and operating time on the removal were explored by an air injected EC reactor. The combined effects of these variables were analyzed by the quadratic model for predicting the highest removal efficiency of arsenic from groundwater. The arsenic removal efficiency was found to be dependent on increase with operating time and concentrations of Ca, Mg, Fe and lower concentration of Mn. When operating variables were considered as minimum operating cost and maximum removal efficiency, the optimum operating parameters were determined to be 132 mg/L of CCa, 55 mg/L of CMg, 4.5 mg /L of CFe, 4.5 mg/L of CMn and operating time of 3 min to meet the target concentration of <10 μg/L. Values of removal efficiency and operating cost at the optimum conditions were 95.1% and 0.041 $/m3

Treatment of textile wastewaters by electrocoagulation: technical and economic evaluation

Bu &ccedil;alışmada, bir tekstil atıksuyunun elektrokoag&uuml;lasyon (EC) ile arıtılmasının sonu&ccedil;ları ortaya konmuştur. Demir ve al&uuml;minyum elektrotlar, monopolar paralel, monopolar seri ve bipolar seri bağlantı şekli ile kullanılmıştır. Arıtma verimliliğinin &ouml;l&ccedil;&uuml;lmesinde KOİ ve t&uuml;rbidite giderimleri dikkate alınmıştır. KOİ gideriminde, her iki elektrot materyalinde asidik ortam daha uygun olup; demir elektrot i&ccedil;in, Bipolar Seri (BP-S) bağlantı şekli etkili olurken, al&uuml;minyum elektrotlarda ise her &uuml;&ccedil; bağlantı şekli i&ccedil;in birbirine yakın sonu&ccedil;lar elde edilmiştir. T&uuml;rbidite gideriminde; optimum pH&rsquo;nın elektrot materyaline bağlı olduğu, al&uuml;minyum elektrotlar i&ccedil;in asidik ortamın, demir elektrotlar i&ccedil;in ise n&ouml;tral ortamın daha uygun olduğu tespit edilmiştir. Genel olarak, y&uuml;ksek akım yoğunluklarının y&uuml;ksek KOİ ve t&uuml;rbidite giderme verimleri sağladığı g&ouml;r&uuml;lm&uuml;şt&uuml;r. D&uuml;ş&uuml;k akım yoğunluğunda (30 A.m-2) demir elektrotlarda sadece Monopolar Paralel (MP-P) sistemden verim alınmıştır. Al&uuml;minyum elektrotlarda ise; KOİ giderimi bağlantı şekline g&ouml;re değişirken, t&uuml;rbidite giderimi bağlantı şeklinden olduk&ccedil;a bağımsızdır. Diğer yandan, EC prosesi al&uuml;minyum elektrotlarla daha hızlı ilerlediğinden; her &uuml;&ccedil; bağlantı i&ccedil;in de 5 dakikalık bir s&uuml;re etkili olurken, demir elektrotlarda ise; seri bağlantı sistemleriyle en az 10 dakikalık bir işlem s&uuml;resine ihtiya&ccedil; duyulmakta, MP-P bağlantı şekli ise daha fazla işlem s&uuml;resi gerektirmektedir. Ekonomik analizde, bir tekstil fabrikasının 1000 m3.g&uuml;n-1 debide atıksuyunun EC ile arıtılmasının işletme giderleri hesaplanmıştır. Sonu&ccedil; olarak, bu &ccedil;alışmada EC prosesinin, kimyasal koag&uuml;lasyona g&ouml;re daha az materyal t&uuml;keten ve daha az &ccedil;amur &uuml;reten, daha hızlı ve daha ekonomik bir proses olduğu belirlenmiştir.&nbsp;Anahtar kelimeler: Ekonomik analiz, elektrokoag&uuml;lasyon, elektrot malzemesi, KOİ, tekstil atıksuları, t&uuml;rbidite.Electrocoagulation (EC) is an effective method for wastewater treatment. This paper presents the results of the treatment of a textile wastewater by EC process. Two electrode materials, aluminium and iron, were connected in three modes namely, monopolar-parallel (MP-P), monopolar-serial (MP-S), and bipolar-serial (BP-S). In MP-P mode; anodes and cathodes are in parallel connection, the current is divided between all the electrodes in relation to the resistance of the individual cells. Hence, a lower potential difference is required in parallel connection, when compared with serial connections. In MP-S configuration; each pair of sacrificial electrodes is internally connected with each other, because the cell voltages sum up, a higher potential difference is required for a given current. Otherwise, in BP-S connection; there is no electrical connection between inner electrodes, only the outer electrodes are connected to the power supply. Outer electrodes are monopolar and inner ones are bipolar. This connection mode has simple setup with and has less maintenance cost during operation. The effects of wastewater pH, current density and operating time are presented separately for two sacrificial electrode materials, Fe and Al, and three electrode connection modes mentioned above.  COD and turbidity removals were selected as performance criteria. The following conclusions may be drawn from the experimental results; acidic medium is preferable for a high COD removal for both electrode materials; iron electrode performs clearly better with BP-S mode, while the performance of aluminium is not strongly dependent on connection mode. For a high turbidity removal, the optimum pH depends on the electrode material; aluminium electrode connected in BP-S mode performs better in acidic medium, while the poor filterability of the flocs dictates pH 7 to be more suitable for the iron electrode connected in MP-S mode. High current density is generally favorable for high COD and turbidity removals in the case of iron; at low current density, MP-P mode performs better, while at high current densities, the three modes perform equally well. In the aluminium case, the effect is more pronounced on COD removal and it depends strongly on the connection mode, but it has nearly a negligible effect on the turbidity removal which also unaffected by the connection mode. In the case of aluminium, steady removal efficiencies are reached within 5 min for all three systems, while for iron electrode, serial connection systems, BP-S and MP-S reach steady values in 10 min, while MP-P needs longer operating time. For a complete technical analysis, it is worth to compare EC with conventional chemical coagulation, in regard with removal efficiencies and various important aspects. For this purpose, jar-tests were performed at laboratory scale in order to determine the adequate coagulant dosage. After choosing the best amount, same experiments have been performed to determine optimum pH value for each coagulant. Experimental conditions, removal efficiencies and some other pertinent data of electrocoagulation and chemical coagulation process variations are shown in text. At first sight, it is clearly seen that EC is faster, consumes less material and produces less sludge than chemical coagulation for similar COD and turbidity removal levels. The process using aluminium electrodes connected in MP-S mode seems to be the best choice. Meanwhile, an economic analysis is, of course, needed for a final selection. In economic analysis; the total operation cost was calculated using various experimental dataset such as; energy consumption, sacrificial electrode material, chemicals and sludge amounts per m3 of wastewater for a textile plant with 1000 m3.day-1 of wastewater. Iron is preferred as a low cost one for electrocogulation. On the other hand, FeCl3 is the preferable salt in view of its techno-economic performance for CC. Finally, when EC and CC are compared both technically and economically, the following results may be drawn; the COD removal performance of CC is 10% higher than EC, the turbidity removal is nearly the same, but in 60% longer retention time. With the same initial pH, the final pH is 7.9 in EC, but 2.9 in CC. The final acidic and chloride bearing medium is an important drawback of CC, causing severe corrosion problems which may necessitate high-cost building materials. From this point, Fe2(SO4)3.7H2O may be used despite of its higher operating cost. High coagulant consumption in CC means high chloride concentration in the effluent. Finally, and more importantly, the operating cost of CC is 3.2 times as high as the operating cost of EC. Keywords: COD, economic analysis, electrocoagulation, electrode material, textile wastewaters, turbidity

Removal of phosphorus from Potato Chips processing wastewater by Electrocoagulation Process: comparison of Electrode Material

Çalışmada, Al ve Fe elektrotlarının kullanıldığı sürekli akışlı elektrokoagülasyon (EK) prosesi ile patatescipsi üretimi atıksularından fosfor giderim verimi araştırılmıştır. pH, akım yoğunluğu ve elektroliz süresigibi fosfor giderim verimini etkileyen işletme parametreleri optimize edilmiştir. Al ve Fe elektrotlarınınkullanıldığı sürekli akışlı EK model reaktörü için optimum hidrolik bekleme süresi sırasıyla, 40 dk ve 60dk, akım yoğunluğu ise her iki elektrot türü için 65 A/m2, çıkış pH değerleri sırasıyla 7,85 ve 8,15 olaraktespit edilmiştir. Bu deneysel koşullarda, 54,4 mg/L olan ham atıksu toplam fosfor konsantrasyonu, Al veFe elektrodunun kullanımı ile sırasıyla 10,4 ve 5,0 mg/L’ye, 45,3 mg/L olan ham atıksu ortofosfatkonsantrasyonu, Al ve Fe elektrodunun kullanımı ile sırasıyla, 5,9 ve 2,9 mg/L’ye düşmüştür. Çıkış pHdeğerlerine bakıldığında elde edilen çıkış suyu pH ayarlamasına gerek kalmaksızın deşarj edilebilirniteliktedir.Sürekli akışlı EK model reaktöründe, elektrot, enerji ve kimyasal maliyetleri dikkate alınarak hesaplananişletme maliyeti Al ve Fe elektrot türleri için sırasıyla, 1,14, 0,76 /m3 olarak tespit edilmiştir. Feelektrodunun, Al elektroduna göre patates cipsi üretim atıksularından fosfor gideriminde daha etkili olduğu,ayrıca, işletme maliyeti analizi sonucunda da Fe elektrot türünün kullanılması ile işletme maliyetinin dahadüşük olduğu belirlenmiştir. Ayrıca, EK prosesinin ortofosfat ve toplam fosfor giderimlerinin 2. derecereaksiyon kinetiğine uyduğu belirlenmiştir.In this study, removal of phosphorus from potato chips processing wastewater by electrocoagulation (EC)process was investigated by using Al and Fe electrodes. Operating parameters affecting phosphorusremoval efficiency such as pH, current density and electrolysis time were optimized. In the EC modelreactor in which either Al or Fe electrodes were used, the optimum hydraulic retention time was found tobe 40 and 60 min, respectively, while the final pH was found to be 7.85 and 8.15, respectively, and thecurrent density was found to be 65 A/m2 for both electrode types. In case of using Al and Fe electrodesunder these experimental conditions, the initial total phosphorus concentration of 54.4 mg/L decreased to10.4 and 5.0 mg/L, respectively, and the initial orthophosphate concentration of 45.3 mg/L decreased to 5.9and 2.9 mg/L, respectively. Considering the final pH value, it can be pointed out that the resultant effluentcan be discharged without any pH adjustment.Considering the costs for electrodes, energy and chemical agents, operating costs for the continuous-flowEC model reactor were found out to be 1.14 and 0.76 per cubic meter wastewater for Al and Fe electrodes,respectively. It was determined that Fe electrodes are more effective than Al electrodes for the removal ofphosphates from potato chips processing wastewaters, and that the operating costs are lower when Feelectrodes are used. It has been determined that the orthophosphate and total phosphorus removal by theEC process is suitable with the second order reaction kinetics

Optimization of arsenic removal from drinking water by electrocoagulation batch process using response surface methodology

In this investigation, arsenic removal from drinking water using electrocoagulation (EC) in a batch mode was studied by response surface methodology (RSM). The RSM was applied to optimize the operating variables viz. current density (CD, A/m2), operating time (tEC, min) and arsenic concentration (Co, µg/L) on arsenic removal in the EC process using iron electrodes. The combined effects of these variables were analyzed by the RSM using quadratic model for predicting the highest removal efficiency of arsenic from drinking water. The proposed model fitted very well with the experimental data. R2 adjusted correlation coefficients (AdjR2: 0.93) for arsenic removal efficiency showed a high significance of the model. The model predicted for a maximum removal of arsenic at the optimum operating conditions (112.3 µg/L, 5.64 A/m2 and 5 min) after the EC process was 93.86% which corresponded to effluent arsenic concentration of 6.9 µg/L. The minimum operating cost (OC) of the EC process was 0.0664 €/m3. This study clearly showed that the RSM was one of the suitable methods for the EC process to optimize the best operating conditions for target value of effluent arsenic concentration (&lt;10 µg/L) while keeping the OC (energy and electrode consumptions) to minimal. © 2013 © 2013 Balaban Desalination Publications.National Council for Scientific Research: BAP-2010-A-21This research work is a part of National Scientific Research Project under contract of BAP-2010-A-21. The authors give thanks to Gebze Institute of Technology for financial support

A mathematical modeling of sulphur dioxide pollution in Erzurum City

A non-linear simple air-quality model was developed by applying the continuity equation for the air control volume over Erzurum city center and tested using daily average values of SO2 and meteorological data obtained during the winter seasons in Erzurum, Turkey from 1994 to 1998. Model parameters are estimated by non-linear regression analysis. Agreement between model predictions and measured data was found very satisfactory with standard deviations less than 20 µg/m3. © 2002 Elsevier Science Ltd. All rights reserved

Adsorption kinetics for the removal of chromium (VI) from aqueous solutions on the activated carbons prepared from agricultural wastes

The batch removal of Cr(VI) from aqueous solution using low-cost adsorbents such as cornelian cherry, apricot stone and almond shell under different experimental conditions was investigated in this study. The influences of initial Cr(VI) ion concentration (20 to 300 mg &#8467;-1), pH (1 to 4) and particle size (0.63 to 1.60 mm) have been reported. Adsorption of Cr(VI) is highly pH-dependent and the results indicate that the optimum pH for the removal was found to be 1 for all types of carbon. A comparison of kinetic models applied to the adsorption of Cr(VI) ions on the adsorbents was evaluated for the pseudo first-order, the pseudo second-order, Elovich and intraparticle diffusion kinetic models, respectively. Results show that the pseudo second-order kinetic model was found to correlate the experimental data well. Keywords: Adsorption, Cr (VI), Adsorption kinetics, Low-cost adsorbents, Aqueous solution WaterSA Vol.30(4) 2004: 533-53

Adsorption Kinetics for the Removal of Nitrite Ions from Aqueous Solutions by an Ion-Exchange Resin

The adsorption kinetics of nitrite ions in aqueous solutions onto an anion-exchange resin A-250 was explored in a well-stirred tank. The capacity of the ion-exchange resin for the removal of nitrite ions from aqueous solution was investigated under different conditions, viz. initial concentration (10–50 mg/l), pH (2–8), particle size (565–850 μm) and resin dosage (2–8 g/l). A number of kinetic models such as those of external and intraparticle diffusion were applied to the results from this study in order to identify the adsorption mechanism. The results correlated well with the intraparticle diffusion model. The experimental parameters had an effect on the effective pore and surface diffusivities. Adsorption of nitrite ions onto the resin showed that the latter could be used as an efficient adsorbent material for the removal of nitrite ions from aqueous solutions

Optimization of some cations for removal of arsenic from groundwater by electrocoagulation process

This study dealt with investigation of arsenic removal from groundwater using electrocoagulation (EC) method in a batch mode by the Box-Behnken experimental design method. Effects of some cations like Ca, Fe, Mg, Mn and operating time on the removal were explored by an air injected EC reactor. The combined effects of these variables were analyzed by the quadratic model for predicting the highest removal efficiency of arsenic from groundwater. The arsenic removal efficiency was found to be dependent on increase with operating time and concentrations of Ca, Mg, Fe and lower concentration of Mn. When operating variables were considered as minimum operating cost and maximum removal efficiency, the optimum operating parameters were determined to be 132 mg/L of CCa, 55 mg/L of CMg, 4.5 mg /L of CFe, 4.5 mg/L of CMn and operating time of 3 min to meet the target concentration of <10 μg/L. Values of removal efficiency and operating cost at the optimum conditions were 95.1% and 0.041 $/m3

Arsenite and arsenate removals from groundwater by electrocoagulation using iron ball anodes: Influence of operating parameters

Removals of arsenite (As(III)) and arsenate (As(V)) from groundwater by a cylindrical packed-bed electrocoagulation (EC) reactor using Fe ball anodes were investigated in this study. Effects of some operating parameters such as initial pH (pHi of 6.5–8.5), applied current (i of 0.075–0.30 A), initial concentration (Co of 30–200 μg/L), diameter of iron ball (dp of 5.0–10.0 mm), height of anode balls in the reactor (h of 2–8 cm) and airflow rate (Qair of 0.0–6.0 L/min) on the removal efficiency of arsenic were evaluated. The removal efficiency of arsenic decreased with increase in concentrations of arsenic from 30 to 200 μg/L while its removal efficiency increased with increase in operating time, applied current, height of anode in the reactor, and airflow rate. The optimum operating conditions for effective As(III) and As(V) removals to meet the permissible level of arsenic effluent concentration of <10 μg/L were determined as 0.3 A, 14 min of EC time for As(III) and 12 min for As(V), a pHi of 7.5, Co of 200 μg/L, dp of 7.5 mm, h of 7.5 cm and Qair of 6 L/min, respectively. Arsenic removal efficiency, energy and electrode consumptions, operating cost, charge loading and arsenic removed capacity per amount of electrochemically generated Fe at the optimum conditions were also calculated as 96.0%, 1.442 kWh/m3, 0.0752 kg/m3, 0.612 $/m3, 252 C and 2.55 μg/mg Fe (0.762 μg/C) for As(III) removal and 95.8$/m3, 216 C and 3.05 μg/mg Fe (0.887 μg/C) for As(V) removal, respectively.TUBITAK (The Scientific and Technical Research Council of Turkey, Project Number = 111Y103

Effect of carrier type on coupled transport kinetics of thiocyanate ions through liquid membranes

Coupled transport of thiocyanate ions through a liquid membrane containing quaternary ammonium chloride salts in chloroform was examined. The influences of the carrier type in the membrane phase on the coupled transport of thiocyanate ions were investigated. The kinetics of the coupled transport were analyzed in the formalism of two consecutive irreversible first-order reactions and the kinetic parameters (k1d, k2m, k2a, Rmmax, tmax, Jdmax, Jamax,) were also calculated. For the coupled transport of thiocyanate ions, quaternary ammonium chloride salts having different carbon atom numbers (Cn) used as carriers were found to increase thiocyanate ions transport efficiency with increasing carbon atom numbers. Tetradecyl trimethylammonium chloride (TDTMACl), hexadecyl trimethylammonium chloride (HDTMACl), and tetraoctyl ammonium chloride (TOACl) were found to be the most effective carrier types for transport of thiocyanate ions when Cn is greater than 16. The activation energies for maximum membrane entrance and exit fluxes were calculated as 32.45 kJ/mol and 34.75 kJ/mol, respectively. The values of the activation energy indicate that the process is controlled by species diffusion